TY - JOUR
T1 - Globular Cluster UVIT Legacy Survey (GlobULeS). III. Omega Centauri in Far-ultraviolet
AU - Prabhu, Deepthi S.
AU - Subramaniam, Annapurni
AU - Sahu, Snehalata
AU - Chung, Chul
AU - Leigh, Nathan W.C.
AU - Dalessandro, Emanuele
AU - Chatterjee, Sourav
AU - Rao, N. Kameswara
AU - Shara, Michael
AU - Côté, Patrick
AU - Choudhury, Samyaday
AU - Pandey, Gajendra
AU - Valcarce, Aldo A.R.
AU - Singh, Gaurav
AU - Postma, Joesph E.
AU - Rani, Sharmila
AU - Bandyopadhyay, Avrajit
AU - Geller, Aaron M.
AU - Hutchings, John
AU - Puzia, Thomas
AU - Simunovic, Mirko
AU - Sohn, Young Jong
AU - Thirupathi, Sivarani
AU - Yadav, Ramakant Singh
N1 - Publisher Copyright:
© 2022. The Author(s). Published by the American Astronomical Society.
PY - 2022/11/1
Y1 - 2022/11/1
N2 - We present the first comprehensive study of the most massive globular cluster, Omega Centauri, in the far-ultraviolet (FUV), extending from the center to ∼28% of the tidal radius using the Ultraviolet Imaging Telescope on board AstroSat. A comparison of the FUV-optical color-magnitude diagrams with available canonical models reveals that horizontal branch (HB) stars bluer than the knee (hHBs) and the white dwarfs (WDs) are fainter in the FUV by ∼0.5 mag than model predictions. They are also fainter than their counterparts in M13, another massive cluster. We simulated HB with at least five subpopulations, including three He-rich populations with a substantial He enrichment of Y up to 0.43 dex, to reproduce the observed FUV distribution. We find the He-rich younger subpopulations to be radially more segregated than the He-normal older ones, suggesting an in situ enrichment from older generations. The ω Cen hHBs span the same T eff range as their M13 counterparts, but some have smaller radii and lower luminosities. This may suggest that a fraction of ω Cen hHBs are less massive than those of M13, similar to the result derived from earlier spectroscopic studies of outer extreme HB stars. The WDs in ω Cen and M13 have similar luminosity-radius-T eff parameters, and 0.44-0.46 M ⊙ He-core WD model tracks evolving from progenitors with Y = 0.4 dex are found to fit the majority of these. This study provides constraints on the formation models of ω Cen based on the estimated range in age, [Fe/H], and Y (in particular) for the HB stars.
AB - We present the first comprehensive study of the most massive globular cluster, Omega Centauri, in the far-ultraviolet (FUV), extending from the center to ∼28% of the tidal radius using the Ultraviolet Imaging Telescope on board AstroSat. A comparison of the FUV-optical color-magnitude diagrams with available canonical models reveals that horizontal branch (HB) stars bluer than the knee (hHBs) and the white dwarfs (WDs) are fainter in the FUV by ∼0.5 mag than model predictions. They are also fainter than their counterparts in M13, another massive cluster. We simulated HB with at least five subpopulations, including three He-rich populations with a substantial He enrichment of Y up to 0.43 dex, to reproduce the observed FUV distribution. We find the He-rich younger subpopulations to be radially more segregated than the He-normal older ones, suggesting an in situ enrichment from older generations. The ω Cen hHBs span the same T eff range as their M13 counterparts, but some have smaller radii and lower luminosities. This may suggest that a fraction of ω Cen hHBs are less massive than those of M13, similar to the result derived from earlier spectroscopic studies of outer extreme HB stars. The WDs in ω Cen and M13 have similar luminosity-radius-T eff parameters, and 0.44-0.46 M ⊙ He-core WD model tracks evolving from progenitors with Y = 0.4 dex are found to fit the majority of these. This study provides constraints on the formation models of ω Cen based on the estimated range in age, [Fe/H], and Y (in particular) for the HB stars.
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U2 - 10.3847/2041-8213/ac9901
DO - 10.3847/2041-8213/ac9901
M3 - Article
AN - SCOPUS:85141855129
SN - 2041-8205
VL - 939
JO - Astrophysical Journal Letters
JF - Astrophysical Journal Letters
IS - 2
M1 - L20
ER -